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Car Forum / Chevrolet / Chevrolet Corvette / April 2007

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4-bolt mains in SB?

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lib - 21 Apr 2007 02:03 GMT
What year did GM begin using 4-Bolt mains in 327ci in stock/production
Corvettes?
Dad - 21 Apr 2007 03:39 GMT
> What year did GM begin using 4-Bolt mains in 327ci in
> stock/production Corvettes?
IIRC the first 4 bolt SB Chevrolet V8 was the 1968/9 Camaro 302. All
mid year 327 Corvette blocks 3782870/3858180/3858174/3892657 were 2
bolt mains up to and including 375 HP. The Corvette 350 in 1969 block
number 3970010 was the first 4bolt with a rare few having 2 bolt. That
same block was a 2 bolt main 327 in 1968 but not used in a Corvette,
The block used for the 302 Camaro was used with 2 bolt mains in 1968
Corvettes. Only one place have I seen it said that a 4 bolt 327
existed and that is block number 3956618 which does not show as a
Corvette 327 block in the Black Book (?).

Simple answer is your '63 is a 2 bolt.

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Dad
05 C6 Silver/Red 6spd Z51
72 Shark Black/Black/4spd
64 Red/red/white top/4spd

lib - 24 Apr 2007 01:28 GMT
Thanx for the info, Dad. I knew mine was a 2-bolt main when I stripped the
block before taking it to the machine shop to be worked over. I was just
curious if the mains had ever became a point of failure when they increased
the HP in the C2- lib

>> What year did GM begin using 4-Bolt mains in 327ci in stock/production
>> Corvettes?
[quoted text clipped - 8 lines]
>
> Simple answer is your '63 is a 2 bolt.
Dad - 24 Apr 2007 14:33 GMT
> Thanx for the info, Dad. I knew mine was a 2-bolt main when I
> stripped the block before taking it to the machine shop to be worked
> over. I was just curious if the mains had ever became a point of
> failure when they increased the HP in the C2- lib

Very defiantly was a weak point of the small block and journal size
was
later increased to stop some of the failures. The quick winding engine
was known for "spinning the mains". It started out life with a 2.30
diameter main, moving up to 2.45 in '68, (302 induced) and finally
2.65
in '70. Under hard acceleration the design allowed the crank to push
against one side of the bearing wiping it clean of any lubricant and
pulling the bearing loose and spinning it with the now scored race.
Lots
of odd shaped parts soon followed.

Dad
05 C6 Silver/Red 6spd Z51
72 Shark Black/Black/4spd
64 Red/red/white top/4spd
Ric Seyler - 25 Apr 2007 16:44 GMT
I don't think there was ever a 4 bolt 327 was there?

>> What year did GM begin using 4-Bolt mains in 327ci in
>> stock/production Corvettes?
[quoted text clipped - 10 lines]
>
> Simple answer is your '63 is a 2 bolt.

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lab~rat  >:-) - 26 Apr 2007 12:42 GMT
>I don't think there was ever a 4 bolt 327 was there?

This site alludes to the idea that it's possible:

http://www.auto-ware.com/techref/CHV_BLK.html

See #3956618

>>> What year did GM begin using 4-Bolt mains in 327ci in
>>> stock/production Corvettes?
[quoted text clipped - 10 lines]
>>
>> Simple answer is your '63 is a 2 bolt.

--
lab~rat  >:-)
Do you want polite or do you want sincere?
Tom in Missouri - 26 Apr 2007 15:17 GMT
While it is possible, it didn't happen. That block was only used as a 4 bolt
in a 302, I'm pretty sure.  I believe it had a problem with a 4 bolt main
and was why the 0010 block came out and basically replaced it.

From the Mortec site:
http://www.mortec.com/castnum.htm

3956618....302.....69....4...Z-28 Camaro
3956618....327...68-69...2
3956618....350.....69....2 or 4
3956632....307.....69....2
3959512....327...62-67...2...Was also used for some "CE" replacement blocks
3959532....283...64......2...Used for some "CE" replacement blocks
3959538....327...........2...Chevy II recessed oil filter boss, Used for
some Chevy II "CE" replacement blocks
3970010....302.....69....4...Z-28 Camaro
3970010....327.....69....2...Trucks and industrial
3970010....350...69-80...2 or 4

While the 327 was built in both small- and large-journal sizes, I don't
believe there have ever been a 4 bolt version from the factory, with the
possible exception of rare heavy duty truck versions such as the little
White single axle tractors. Since they were a heavy duty application, they
_MAY_ have had a 4 bolt main but I don't know.

Now on that point, there is nothing to prevent taking a 4 bolt LJ block and
dropping a LJ 327 crank into it with proper pistons and creating a 4 bolt
327 that would look completely factory.  The only issue is I don't know of a
steel forged LJ 327 crank, only cast LJ 327 cranks.

>>I don't think there was ever a 4 bolt 327 was there?
>
[quoted text clipped - 22 lines]
> lab~rat  >:-)
> Do you want polite or do you want sincere?
lab~rat  >:-) - 27 Apr 2007 14:37 GMT
>While it is possible, it didn't happen. That block was only used as a 4 bolt
>in a 302, I'm pretty sure.  I believe it had a problem with a 4 bolt main
[quoted text clipped - 25 lines]
>327 that would look completely factory.  The only issue is I don't know of a
>steel forged LJ 327 crank, only cast LJ 327 cranks.

And that would be a beautiful thing...
--
lab~rat  >:-)
Do you want polite or do you want sincere?
Eugene Blanchard - 28 Apr 2007 05:40 GMT
The Chevy V8 Engine Casting book doesn't list a 4 bolt main 327.

>>While it is possible, it didn't happen. That block was only used as a 4
>>bolt
[quoted text clipped - 32 lines]
> lab~rat  >:-)
> Do you want polite or do you want sincere?

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Eugene Blanchard
http://www.catsasskustoms.com
Parts, Performance, Passion
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